Sometimes they are picky eaters. At 2 years old he should be mainly on salads, but I'd try rotating the roaches in along with a variety of bugs every few days and see if the variety will get his interest. You could also make a game of it and try to get him to chase them across the floor or something like that. I used to take the screen top from a tank and put them on the screen so they'd walk around vertically and that seemed to get more attention from my dragon. I've also seen videos of people putting them inside plastic cat toy balls so they were a little more work to get to.